The objective is to study the pharmacological effects and chemical nature of naturally occurring, water-soluble, biologically active substances from marine nudibranchs (Gastropoda). Preliminary work indicates that these toxins have unusual hypotensive and cardiac effects in mammals. Standard methods of isolation would be used including dialysis, column chromatography, high speed liquid chromatography and preparative electrophoresis. Attempts will be made to establish the chemical structure by classical methods. Purified preparations would be used for pharmacological studies to determine the site and mechanism of action of the active substance. Both whole animal (anesthetized rat) and isolated organ preparations would be used. The latter would include guinea pig auricles, electrically driven ventricular muscle strips, Langendorff perfused hearts and smooth muscle (ileum).